Precast Concrete Beam with Open Flanges and Diaphragms
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Solution Overview
Problem
Super-Tee beams used in bridge construction are heavy and have internal cavities that hinder inspectability and require different sizes for varying requirements, leading to weight and cost penalties, while conventional Tee beams lack the structural improvements of Super-Tee beams.
Innovation Solution
A precast concrete beam design featuring a substantially planar web with laterally extending flanges and diaphragms spaced to support loads, allowing for thinner and wider flanges without the weight penalty of a box-section configuration, and incorporating prestressed reinforcement and an enlarged bulb for enhanced structural performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If Super-Tee beam configuration is used, then beam width and torsional rigidity are improved, but weight increases substantially
Solution Approach 1:
The beam is divided into a web portion and separate flange elements that are not fully enclosed. The flanges are open at the top rather than forming a closed box-section, segmenting the structure to reduce weight while maintaining width capability.
Solution Approach 2:
The flanges have varying thicknesses with different local properties - thicker at the root for strength and thinner at the free end for weight reduction. This local quality variation allows the beam to achieve required width while minimizing overall weight.
2Strength
If closed-flange Super-Tee configuration is used, then torsional rigidity is improved, but inspectability deteriorates due to enclosed internal cavity
Solution Approach 1:
The top closure of the flange is removed or extracted from the structure, converting the closed box-section into an open-flange configuration. This extraction eliminates the enclosed internal cavity, allowing inspection access while maintaining sufficient torsional rigidity through the web and flange root connections.
Solution Approach 2:
The web acts as an intermediary structural element that provides torsional resistance without requiring full flange enclosure. The web-flange connections serve as mediators that transfer loads and maintain rigidity while allowing the flange opening for inspection access.
3Strength
If different Super-Tee beam sizes are provided for different requirements, then structural performance is optimized, but manufacturing complexity and cost increase
Solution Approach 1:
The beam design incorporates adjustable or modular flange elements that can be configured for different span and load requirements using the same basic manufacturing process. The standardized web and flange root design with adjustable flange dimensions provides multi-functionality across different application scenarios.
Solution Approach 2:
The beam dimensions, particularly flange width and thickness, are varied as parameters within a standardized design framework rather than creating entirely different beam types. This parameter change approach allows optimization for different requirements while maintaining manufacturing standardization.
4Ease of manufacture
If conventional Tee beam configuration is used, then manufacturing simplicity is maintained, but beam width and torsional rigidity are limited
Solution Approach 1:
The beam design transitions from the conventional narrow Tee shape to a wider configuration by developing the flange dimension laterally. This dimensional change in the horizontal plane increases beam width and torsional rigidity while maintaining the relatively simple casting process through standardized mold designs.
Data Source
AI summary
A precast concrete beam including a substantially planar web extending longitudinally between ends of the beam; a pair of flanges formed integrally with the web, each flange extending laterally from an elongate edge of the web and extending longitudinally between the ends of the beam so as to define a structure engaging surface of the beam; and a plurality of diaphragms formed integrally with the web and the flanges, each diaphragm spanning laterally between a side of the web and one of the flanges, wherein the diaphragms are spaced apart along the beam to thereby support the flanges.